1. Field of the Invention
The present invention relates to band wheels for band saws and more particularly to band wheels of the flanged type with replaceable wear surfaces.
2. Description of the Prior Art
In band saw machines of the type for which the present invention is intended, the cutting band or blade is trained in tension around the peripheral surfaces of two or more spaced band wheels which rotate about substantially parallel axes. Band wheels for such machines are conventionally either crowned wheels or flanged wheels and the flanged wheels have either resilient tires or metal tires. Resilient tire wheels of both the crowned and flanged type have a distinct disadvantage in that, on heavy duty, high production band saw machines where cutting fluids are used, the cutting band will slip off the resilient tire and off the band wheel when subjected to high tension and heavy feed forces. Because of this severe limitation, heavy duty, high production band saw machines have heretofore employed band wheels with metal tires, the most satisfactory but most expensive of which are hardened metal tires.
In the use of band saw machines having flanged band wheels with metal tires, chips and scale from cutting operations frequently lodge between the cutting band and the metal tire causing abrasive wear on the tire. Since the concentration of chips and scale is greater nearer the cutting edge of the cutting band, the abrasive wear on the metal tire is more severe near the non-flanged front face, causing a taper of the cutting band contact surface. More rapid wear of the metal tire occurs if the feed is too great for the material being cut, causing the cutting band to stick in the workpiece and slip on the powered band wheel while the powered band wheel continues to rotate. This wear of the metal tires of band wheels, in heavy duty high production type band saw machines, is a significant and troublesome problem.
When the surface of the metal tire becomes worn and tapered as a result of abrasion and wear due to slippage, uneven stresses occur in the cutting band while it is trained under high tension over and caused to conform to the metal tire surface. These uneven stresses have a detrimental effect on the fatigue life or flex life of the cutting band. Consequently, it is imperative that the cutting band contact surface be periodically restored or replaced. It is therefore desirable that the cutting band contact surface be readily replaceable.
There have been numerous attempts to make replaceable cutting band contact surfaces for flanged band wheels with metal contact surfaces or tires. These attempts include the use of hardened steel hoops which must be machined to close tolerences and pressed on the band wheel peripheral surface or installed by conventional heat shrinking techniques. The costs and difficulty involved in production of band wheels and hardened steel hoops by precise machine operations and the fitting of such hardened steel hoops by the techniques mentioned are a major concern. Moreover, these and other similar techniques, while avoiding the need for replacement of the entire band wheel, are unsatisfactory in that special equipment is required for manufacture and replacement, and the band wheel generally must be removed from the machine users plant for replacement of the cutting band contact surface. Thus, existing solutions are neither acceptable nor economical and are unsatisfactory for replacement service in the machine users plant.
It would therefore be an important and desirable advance in the art to provide a band wheel having a readily replaceable and improved cutting band contact surface which is suited for heavy duty, high production applications.
In the course of band saw machine operation, wear also occurs on the front surface of the flange of the band wheel where the cutting band contacts the flange. While this wear is thought to have little affect on the fatigue life or flex life of the cutting band, this flange surface often plays an important part in alignment and it would therefore be a desirable advance in the art to provide a band wheel with a readily replaceable flange.